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Re: Copper Banding?

Original poster: "Gerald  Reynolds" <gerryreynolds@xxxxxxxxxxxxx>

Hi Antonio,

My interpretation of what you say below is that because the pitch of the banded spiral is smaller (and the primary coil is more compact as a result) the inductance will be larger that a spread out spiral made from CU tubing. Also, if we are comparing two spirals made with 50ft of conductor and they both start with the same inside diameter, the banded spiral will have more turns than the 50 ft tubed spiral. Or, are we comparing the same number of turns?

Gerry R.

Original poster: "Antonio Carlos M. de Queiroz" <acmdq@xxxxxxxxxx>

The reason is that a flat spiral made with tape acts as a stack of coupled filamental coils. If the coupling were unitary, the inductance
would be the same of a single filament. But as the coupling between distant filaments is smaller than one, the inductance decreases.
Consider for example two parallel filamental coils with inductance L.
If they are at small distance, they act as a single coil with inductance
L. If they are far apart, the coupling between them is insignificant,
and the total inductance falls to L/2.

Antonio Carlos M. de Queiroz